CD22202 View Datasheet(PDF) - Intersil
Part Name
Description
Manufacturer
CD22202 Datasheet PDF : 6 Pages
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CD22202, CD22203
into the audio spectrum, so if excessive noise is present
above 28kHz, the simple RC filter shown below may be
used to band limit the incoming signal. The cut off
frequency is 3.9kHz.
NOISY
SIGNAL
270kΩ
0.0015µF
ANALOG
IN
33kΩ
CD22202
CD22203
FIGURE 4. FILTER FOR USE IN EXTREME HIGH FREQUENCY
INPUT NOISE ENVIRONMENT
Noise will also be reduced by placing a grounded trace
around XIN and XOUT pins on the circuit board layout when
using a crystal. It is important to note that XOUT is not
intended to drive an additional device. XIN may be driven
externally; in this case, leave XOUT floating.
Timing Waveforms
TONE BURST 1
tON
tOFF
ANALOG
INPUT
D1, D2
D4, D8
PAUSE TONE BURST 2
tR
tD
tSU
tH
tCL
PARAMETER
SYMBOL MIN TYP MAX UNITS
Tone Time
For Detection
tON
For Rejection
tON
Pause Time
For Detection
tOFF
For Rejection
tOFF
Detect Time
tD
Release Time
tR
Data Setup Time
tSU
Data Hold Time
tH
DV Clear Time
tCL
CLRDV Pulse Width
tPW
ED Detect Time
tED
ED Release Time
tER
Output Enable Time
-
CL = 50pF, RL = 1kΩ
Output Disable Time
-
CL = 35pF, RL = 500Ω
Output Rise Time
-
CL = 50pF
Output Fall Time
-
CL = 50pF
40
-
-
ms
-
-
20
ms
40
-
-
ms
-
-
20
ms
25
-
46
ms
35
50 ms
7
-
-
µs
4.2 -
5
ms
- 160 250 ns
200 -
-
ns
7
-
22
ms
2
-
18
ms
- 200 300 ns
- 150 200 ns
- 200 300 ns
- 160 250 ns
DV
tPW
CLRDV
tED
tER
ED
(NOTE)
NOTE: Early Detect output is available only on the CD22203.
FIGURE 5.
Guard Time
Whenever the DTMF receiver is continually monitoring a
voice channel containing distorted or musical voices or
tones, additional guard time may be added in order to
prevent false decoding. This may be done in software by
verifying that both ED and DV are present simultaneously for
about 55ms. An appropriate guard time should be selected
to balance the fastest expected dialing speed against the
rejection of distorted or musical voices or tones (most
autodialers operate in the 65ms to 75ms range although a
few generate 50ms tones). A hardware guard time circuit is
shown in Figure 6. R3 and R4 should keep the voice
amplitude as low as practical, while R2 and R5 adjust
detection speed.
5
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